[PATCH v2 1/6] mtd: ubi: Do not zero out EC and VID on ECC-ed NOR flashes

[tkuw584924 at gmail.com]

From: Takahiro Kuwano <Takahiro.Kuwano at infineon.com>

For NOR flashes EC and VID are zeroed out before an erase is issued to
make sure UBI does not mistakenly treat the PEB as used and associate it
with an LEB.

But on some flashes, like the Infineon Semper NOR flash family,
multi-pass page programming is not allowed on the default ECC scheme.
This means zeroing out these magic numbers will result in the flash
throwing a page programming error.

Do not zero out EC and VID for such flashes. A writesize > 1 is an
indication of an ECC-ed flash.

This patch replicates the following upstream linux commit:
f669e74be820 ("ubi: Do not zero out EC and VID on ECC-ed NOR flashes")

Acked-by: Tudor Ambarus <tudor.ambarus at linaro.org>
Signed-off-by: Takahiro Kuwano <Takahiro.Kuwano at infineon.com>
---
 drivers/mtd/ubi/build.c | 4 +---
 drivers/mtd/ubi/io.c    | 9 ++++++++-
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/mtd/ubi/build.c b/drivers/mtd/ubi/build.c
index a1941b8eb8..81c1b7bdbc 100644
--- a/drivers/mtd/ubi/build.c
+++ b/drivers/mtd/ubi/build.c
@@ -679,10 +679,8 @@ static int io_init(struct ubi_device *ubi, int max_beb_per1024)
 		ubi->bad_peb_limit = get_bad_peb_limit(ubi, max_beb_per1024);
 	}
 
-	if (ubi->mtd->type == MTD_NORFLASH) {
-		ubi_assert(ubi->mtd->writesize == 1);
+	if (ubi->mtd->type == MTD_NORFLASH)
 		ubi->nor_flash = 1;
-	}
 
 	ubi->min_io_size = ubi->mtd->writesize;
 	ubi->hdrs_min_io_size = ubi->mtd->writesize >> ubi->mtd->subpage_sft;
diff --git a/drivers/mtd/ubi/io.c b/drivers/mtd/ubi/io.c
index 14be95b74b..45699b4a47 100644
--- a/drivers/mtd/ubi/io.c
+++ b/drivers/mtd/ubi/io.c
@@ -563,7 +563,14 @@ int ubi_io_sync_erase(struct ubi_device *ubi, int pnum, int torture)
 		return -EROFS;
 	}
 
-	if (ubi->nor_flash) {
+	/*
+	 * If the flash is ECC-ed then we have to erase the ECC block before we
+	 * can write to it. But the write is in preparation to an erase in the
+	 * first place. This means we cannot zero out EC and VID before the
+	 * erase and we just have to hope the flash starts erasing from the
+	 * start of the page.
+	 */
+	if (ubi->nor_flash && ubi->mtd->writesize == 1) {
 		err = nor_erase_prepare(ubi, pnum);
 		if (err)
 			return err;
-- 
2.34.1